System and method for gain regulation

Abstract

Disclosed herein is a system for fast gain regulation in a gamma-ray spectroscopy instrument. The system includes a detector configured to generate a signal indicative of energy arriving at the detector, and a processor configured to determine one or more system performance indicators. The system also includes a controller configured to compute a first gain correction term based on one of more system performance indicators and change the device gain based on the computed first gain correction term.

What is claimed is: 
     
       1. A gamma-ray spectroscopy system comprising:
 a detector configured to generate a signal indicative of energy arriving at the detector; and 
 a controller comprising a processor configured to:
 determine one or more system performance indicators; 
 compute a first gain correction term based on the one or more system performance indicators over a first time period; 
 identify one or more measured spectral features based on the signal; 
 compute a second gain correction term based on the one or more measured spectral features over a second time period; and 
 adjust a device gain of the gamma-ray spectroscopy system based on a combination of the first gain correction and the second gain correction determined at each conclusion of the first time period. 
 
 
     
     
       2. The system of  claim 1 , wherein the one or more system performance indicators comprises an indication of system performance obtained more quickly than the one or more measured spectral features are identified. 
     
     
       3. The system of  claim 2 , wherein the system performance indicator is obtained approximately every 125 milliseconds and the measured spectral features are identified approximately every 10 seconds. 
     
     
       4. The system of  claim 1 , wherein the controller computes the first gain correction term concurrently at a first rate while computing the second gain correction term at a slower second rate. 
     
     
       5. The system of  claim 1 , wherein the one or more system performance indicators comprises a total count rate at the detector, peak count rate at the detector, average detector current, a peak detector current, or a combination thereof. 
     
     
       6. The system of  claim 1 , wherein the combination comprises the first gain correction term added to the second gain correction term to result in an amount by which the device gain is adjusted. 
     
     
       7. The system of  claim 1 , wherein the combination comprises the second gain correction term mathematically manipulated by the first gain correction term to result in an amount by which the device gain is adjusted. 
     
     
       8. The system of  claim 1 , further comprising an amplifying device coupled to the detector, wherein the controller is further configured to adjust the device gain by changing a gain of the amplifying device configured to amplify the signal output from the detector. 
     
     
       9. The system of  claim 1 , wherein the controller is further configured to adjust the device gain by redistributing the signal indicative of energy arriving at the detector digitally into a plurality of bins of a spectral histogram. 
     
     
       10. The system of  claim 1 , the detector further comprising a scintillator and photomultiplier, wherein the controller is further configured to change the device gain by increasing or decreasing a voltage applied at the photomultiplier. 
     
     
       11. The system of  claim 10 , wherein the one or more system performance indicators comprises a peak current in the photomultiplier or a peak count rate in the photomultiplier. 
     
     
       12. The system of  claim 1 , wherein the one or more system performance indicators comprises an average photomultiplier current in a sampling interval. 
     
     
       13. The system of  claim 1 , wherein the one or more system performance indicators comprises an average count rate of the detector over a sampling interval. 
     
     
       14. The system of  claim 1 , wherein the one or more system performance indicators comprises an average count rate multiplied by an average observed deposited energy. 
     
     
       15. The system according to  claim 1 , wherein a relationship between the first gain correction term and a given one of the one or more system performance indicators is pre-determined or determined dynamically. 
     
     
       16. A system comprising a gamma-ray spectroscopy instrument comprising:
 a detector configured to generate a signal indicative of energy arriving at the detector; 
 a controller comprising a processor configured to:
 determine one or more system performance indicators and one or more measured spectral features; 
 generate a combined gain adjustment of an open-loop gain adjustment and a closed-loop gain adjustment, wherein the open-loop gain adjustment is based on the one or more system performance indicators and the closed-loop gain adjustment is based on the one or more measured spectral features; and 
 adjust a device gain of the gamma-ray spectroscopy instrument based at least in part on the combined gain adjustment. 
 
 
     
     
       17. The system of  claim 16 , wherein the open-loop gain adjustment is generated over a first time period, and the closed-loop gain adjustment is generated over a second time period, wherein the first time period is shorter than the second time period. 
     
     
       18. The system of  claim 17 , wherein the first time period is approximately 125 milliseconds and the second time period is approximately every 10 seconds. 
     
     
       19. The system of  claim 16 , wherein the closed-loop gain adjustment is generated at a slower rate than the open-loop gain adjustment. 
     
     
       20. The system of  claim 19 , wherein the closed-loop gain adjustment is performed at rate approximately two orders of magnitude slower than the open-loop gain adjustment.